Disabling electrical connections using pass-through 3D interconnects and associated systems and methods

ABSTRACT

Pass-through 3D interconnects and microelectronic dies and systems of stacked dies that include such interconnects to disable electrical connections are disclosed herein. In one embodiment, a system of stacked dies includes a first microelectronic die having a backside, an interconnect extending through the first die to the backside, an integrated circuit electrically coupled to the interconnect, and a first electrostatic discharge (ESD) device electrically isolated from the interconnect. A second microelectronic die has a front side coupled to the backside of the first die, a metal contact at the front side electrically coupled to the interconnect, and a second ESD device electrically coupled to the metal contact. In another embodiment, the first die further includes a substrate carrying the integrated circuit and the first ESD device, and the interconnect is positioned in the substrate to disable an electrical connection between the first ESD device and the interconnect.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/850,803 filed Mar. 26, 2013, now U.S. Pat. No. 8,772,086, which is acontinuation of U.S. application Ser. No. 13/572,461 filed Aug. 10,2012, now U.S. Pat. No. 8,404,521, which is a divisional of U.S.application Ser. No. 12/121,654 filed May 15, 2008, now U.S. Pat. No.8,253,230, each of which is incorporated herein by reference in itsentirety.

TECHNICAL FIELD

The present disclosure is directed generally to microelectronic diepackages, and more particularly to stacked microelectronic dies havingthrough-die or through-layer interconnects.

BACKGROUND

Packaged microelectronic assemblies, such as memory chips andmicroprocessor chips, typically include a microelectronic die mounted toa substrate and encased in a plastic protective covering. The dieincludes functional features, such as memory cells, processor circuits,and interconnecting circuitry. The die also typically includes bond padselectrically coupled to the functional features. The bond pads areelectrically connected to pins or other types of terminals that extendoutside the protective covering for connecting the die to busses,circuits, or other microelectronic assemblies. In one conventionalarrangement, the die is mounted (face down) to a supporting substrate(e.g., a printed circuit board), and the die bond pads are electricallycoupled to corresponding bond pads of the substrate with metal bumps(e.g., solder balls or other suitable connections). After encapsulation,a ball-grid array on the backside of the substrate or other arrays ofadditional metal bumps can electrically connect the substrate to one ormore external devices. Accordingly, the substrate supports the die andelectrically connects the die to the external devices.

Die manufacturers have come under increasing pressure to reduce thevolume occupied by the dies and yet increase the capacity of theresulting encapsulated assemblies. To meet these demands, diemanufacturers often stack multiple dies on top of each other to increasethe capacity or performance of the device within the limited surfacearea on the circuit board or other element to which the dies aremounted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional side view of a system of stackedmicroelectronic dies having electrostatic discharge componentsconfigured in accordance with an embodiment of the disclosure.

FIG. 1B is a schematic view of a system of stacked microelectronic diesin accordance with an embodiment of the disclosure.

FIGS. 2A-F illustrate stages of methods for forming the system of FIG.1A in accordance with several embodiments of the disclosure.

FIG. 3 is a cross-sectional side view of a microelectronic workpiececonfigured in accordance with another embodiment of the disclosure.

FIG. 4 is a cross-sectional side view of a microelectronic workpiececonfigured in accordance with yet another embodiment of the disclosure.

FIG. 5 is a schematic illustration of a system in which embodiments ofmicroelectronic dies having electrostatic discharge components withdisabled electrical connections may be incorporated.

DETAILED DESCRIPTION

Various embodiments of pass-through 3D interconnects, such asthrough-die or through-silicon vias, and microelectronic dies and/orsystems of dies that include such interconnects are described below. Theterm “interconnect” may encompass various types of conductive structuresthat extend at least partially through a substrate of a microelectronicdie and electrically couple together conductive contacts located atopposing ends of the interconnect. The term “substrate” may encompassany of a variety of conductive and/or nonconductive layers (e.g.,metallic, semi-conductive, and/or dielectric materials) that aresituated upon and/or within one another. Such substrates can include anyof a myriad of electrical devices (e.g., transistors, resistors,capacitors, etc.) or systems of such devices (e.g., an integratedcircuit, a memory, a processor, etc.) formed in the conductive and/ornonconductive layers of an individual substrate. Other embodiments ofpass-through interconnects, substrates, and microelectronic dies and/orsystems of dies that include such interconnects and substrates, inaddition to or in lieu of the embodiments described in this section, mayhave several additional features or may not include many of the featuresshown and described below with reference to FIGS. 1-5.

FIG. 1A is a cross-sectional side view of an embodiment of a system 100having a first microelectronic die 101 and a second microelectronic die102 stacked on the first die 101. The first die 101 includes a firstsubstrate 110 a, a plurality of pass-through 3D interconnects 120extending through the first substrate 110 a, and a first integratedcircuit 130 a electrically coupled to the interconnects 120. The firstsubstrate 110 a can be a silicon substrate or another suitablesemiconductor substrate. The first integrated circuit 130 a is shownschematically, and it will be appreciated that the first integratedcircuit 130 a is within a large portion of the first substrate 110 a.The first die 101 can also include a plurality of first substrate pads112 a located at corresponding interconnects 120 and electricallycoupled to the first integrated circuit 130 a. In the embodiment shownin FIG. 1A, the first die 101 further includes dielectric liners 122along the interconnects 120, a backside dielectric layer 114 defining abackside surface 115, and a redistribution layer (RDL) 140 having RDLtraces 142 with contacts 144. The dielectric liners 122 electricallyisolate the individual interconnects 120 from the first substrate 110 aand the first substrate pads 112 a, and the RDL traces 142 electricallycouple the first substrate pads 112 a and the correspondinginterconnects 120 to the contacts 144.

The second die 102 can have a second substrate 110 b with second contactpads 112 b and a front side structure 180 having front side contacts 184arranged in the pattern of the interconnects 120 of the first die 101.The second die 102 can also optionally include a second integratedcircuit 130 b electrically coupled to the second substrate pads 112 b.The second substrate 110 b can also be a silicon substrate or anothersuitable semiconductor substrate, and the second integrated circuit 130b is also shown schematically and can be within a large portion of thesecond substrate 110 b. In many embodiments, metal bonds 166 canelectrically coupled the front side contacts 184 of the second die 102to corresponding interconnects 120 of the first die 101. In otherembodiments, electrical connectors, such as solder balls, can be used inlieu of the metal bonds 166.

FIG. 1B schematically illustrates an embodiment of the first and secondintegrated circuits 130 a-b in greater detail. The first integratedcircuit 130 a of the first die 101 can include internal circuitry 131 aand a first electrostatic discharge system 150 a, and the secondintegrated circuit 130 b of the second die 102 can include internalcircuitry 131 b and a second electrostatic discharge system 150 b. Thefirst electrostatic discharge system 150 a can include one or more firstelectrostatic discharge (ESD) devices 151 a, and the first ESD devices151 a can include temporary ESD devices and/or permanent ESD devicesdepending on the application. For example, the temporary first ESDdevices 151 a can be current ESD devices (ESDi) that are temporarilycoupled to the first substrate pad 112 a and power or ground, and thepermanent first ESD devices 151 a can be voltage ESD devices (ESDV)coupled to the first substrate pad 112 a via a resistor 153 a and theinternal circuitry 131 a. The second electrostatic discharge system 150b can include one or more second ESD devices 151 b that can includecurrent ESD devices (ESDi) coupled by lines 154 and voltage ESD devices(ESDV) coupled via a resistor 155 b; in many embodiments all of thesecond ESD devices 151 b remain electrically coupled to internalcircuitry. In many applications, the electrostatic discharge systems 150a-b have one or more ESD devices associated with each substrate pad(e.g., one or more current and/or voltage ESD device for each substratepad).

Referring to FIGS. 1A and 1B together, selected first ESD devices 151 aare electrically isolated from the other components of the firstintegrated circuit 130 a at one or more stages of the fabricationprocess. For example, in the specific embodiment shown in FIG. 1B, theESDi devices have been electrically isolated from the substrate pad 112a and interconnect 120, but ESDV devices remain electrically connectedto the internal circuitry 131 a. In other embodiments, all of the firstESD devices 151 a can be temporary devices that are eventuallydisconnected from the other components of the first integrated circuit130 a.

Referring to FIG. 1A, the selected first ESD devices 151 a can beelectrically isolated from the other components of the first integratedcircuit 130 a by forming the dielectric liners 122 between the selectedfirst ESD devices 151 a and the interconnects 120. For example, adielectric liner 122 can be formed to cause a break in a line 154 thatpreviously connected a selected first ESD device 151 a to acorresponding first substrate pad 112 a. As such, selected first ESDdevices 151 a can be effectively disabled or disconnected in thepackaged system 100. In other embodiments, all of the first ESD devices151 a can be electrically disconnected or disabled at one or more stagesof the fabrication process.

Unlike the first die 101, however, the second ESD devices 151 b are notelectrically isolated from an integrated circuit. The second ESD devices151 b can remain electrically coupled to the other components of thesecond integrated circuit 130 b, and the second ESD devices 151 b canalso be electrically coupled to the first integrated circuit 130 a via aconductive path that includes an individual contact 184, a conductivelayer 185, an individual metal bond 166, and an individual interconnect120. In other embodiments, the second ESD devices 151 b can be separatecomponents in the second die 102 that are not electrically coupled tothe second integrated circuit 130 b.

In general, the ESD systems 150 a-b are configured to protect anintegrated circuit from an ESD event. An ESD event typically involvesthe transfer of energy between an integrated circuit and another bodythat is at a different electrical potential than the integrated circuit.For example, during the manufacturing of the second die 102, anequipment operator can inadvertently touch and transfer an electrostaticpotential to one of the substrate pads 112 b. Without the protection ofthe second ESD system 150 b, the transferred electrostatic potential candeliver a large electrical charge that could damage charge-sensitiveportions of the second integrated circuit 130 b. Even without makingphysical contact with a substrate pad, ESD events can also be caused byionized ambient discharges (e.g., sparks) between a substrate pad andother charged bodies brought into close proximity with the substratepad.

Embodiments of the ESD systems 150 a-b can include circuit elements thatdivert potentially damaging charges away from a corresponding integratedcircuit and/or charge-sensitive portions of the integrated circuit. Inmany embodiments, individual ESD devices include one or more diodes,metal-oxide-silicon (MOS) devices, and/or silicon-controlled rectifiers(SCRs) that are electrically coupled with a corresponding integratedcircuit. In the specific embodiments of FIGS. 1A and 1B, the second ESDdevices 151 b are components of the second integrated circuit 130 b andin a parallel circuit configuration with the first integrated circuit130 a. The selected first ESD devices 151 a that have been disabled, onthe other hand, do not provide ESD protection to the first integratedcircuit 130 a or the second integrated circuit 130 b when the system 100is completely finished. However, before breaking the electricalconnections 154 associated with the selected first ESD devices 151 a,the selected first ESD devices 151 a can provide temporary ESDprotection to the first integrated circuit 130 a. The connections 154associated with the selected or temporary first ESD devices 151 a can bedisabled prior to (or during) the assembly of the system 100. In manyembodiments, disabling the electrical connections associated with theselected first ESD devices 151 a can be carried out when forming theinterconnects 120, and in this case the first ESD devices 151 a thatremain electrically coupled to the first integrated circuit can protectthe first integrated circuit during formation of the interconnects 120(e.g., the ESDV devices shown in FIG. 1B).

In contrast to the system 100, conventional dies in stacked packagestypically have an ESD device dedicated to each connection between asubstrate pad and an integrated circuit. The ESD devices at one level ofthe conventional die stack are coupled to the ESD devices at anotherlevel of the conventional die stack. This creates multiple levels of ESDdevices interconnected with one another. In general, a large number ofESD devices are redundant, and a single ESD device for each group ofinterconnected substrate pads is sufficient for protecting integratedcircuits at all levels of the die stack. Removing or disabling ESDdevices from only some of these dies and not others would require thatthe dies have a different configuration of integrated circuitry. Thiswould accordingly require die manufacturers to fabricate separateworkpieces to create the different integrated circuits. Thus, packagemanufacturers typically do not selectively disable or remove ESDdevices. Unfortunately, as the performance of devices increases, diepackages with redundant ESD devices can impair performance because thecomponents of ESD devices typically introduce a signal delay, andintercoupling multiple ESD devices can exacerbate the signal delay.

Embodiments of the system 100, however, overcome the tradeoff betweenoverall performance and manufacturing costs. In many embodiments,electrical connections with ESD devices can be disabled at little or noadditional cost such that the system 100 does not employ redundant ESDdevices. In several embodiments, the ESD devices can be selectivelydisable in the normal process of fabrication interconnects by formingselected interconnects through one or more metal layers, traces, and/orvias that complete the temporary conductive path between an ESD deviceand an integrated circuit. This process not only forms the interconnectbut also removes conductive material to disconnect or otherwise disablethe ESD device at the same time. In additional embodiments, electricalisolation can also be provided by a dielectric layer that separates theinterconnect from the substrate.

Embodiments of the system 100 can also include a dielectric casing 198encapsulating the first and second dies 101 and 102 and an interposersubstrate 190 carrying the first and second dies 101 and 102. Theinterposer substrate 190, for example, can be a printed circuit board orother substrate that includes die bond pads 192 and package bond pads194 electrically coupled to the die bond pads 192 through the interposersubstrate 190. In several embodiments, individual bump bonds 196 orother electrical connectors are aligned with and attached to individualRDL contacts 144 of the first die 101 and individual die bond pads 192of the interposer substrate 190. Accordingly, individual package bondpads 194 can provide an electrical coupling to the first integratedcircuit 130 a of the first die 101, the second integrated circuit 130 b,and the second ESD devices 151 b of the second die 102.

FIGS. 2A-F illustrate stages of methods for forming the system 100 andselectively disabling electrical connections with ESD devices inaccordance with several embodiments of the disclosure. FIG. 2A is across-sectional side view of a microelectronic workpiece 202 (e.g., asemiconductor or microelectronic wafer) at a stage of forming anembodiment of the first die 101. The workpiece 202 includes the firstsubstrate 110 a, the internal circuitry 131 a, selected first ESDdevices 151 a, and corresponding first substrate pads 112 a. In theembodiment of FIG. 2A, the internal circuitry 131 a is electricallycoupled to a first metal layer 211 and the first ESD devices 151 a areelectrically coupled to a second metal layer 213. The first metal layer211 can be electrically coupled to the second metal layer 213 byconductive vias 215, and thus the first ESD devices 151 a areelectrically coupled to the internal circuitry 131 a at this stage ofthe process. The workpiece 202 also includes second vias 217 thatelectrically couple the internal circuitry 131 a and the first ESDdevices 151 a to the first substrate pads 112 a.

In many embodiments, the first metal layer 211, the second metal layer213, the first vias 215, and the second via 217 are formed during a backend of the line (BEOL) process. For example, the first and second metallayers 211 and 213 can include aluminum, copper, or another metal thathas been formed above semiconductor devices (not shown) of theintegrated circuit. This metal can be patterned to define electricalconnections of the integrated circuit and can include passivation layers(not shown) that separate individual levels of metal from one another.The first and second vias 215 and 217 can also be formed in a BEOLprocess and can include a metallic material (e.g., copper or tungsten).The vias 215 and 217 can extend through individual passivation layers toprovide the electrical couplings between (a) the first and second metallayers 211 and 213 and (b) the first metal layer 211 and the firstsubstrate pads 112 a. In additional or alternative embodiments, otherarrangements of vias or interconnect structures can be used tointerconnect metal layers and substrate pads. For example, two or morevias can couple the first metal layer 211 to the substrate pad 144and/or a single via can couple the first metal layer 211 to the secondmetal layer 213. Further, the number of vias and interconnect structurescan also be based on the magnitude of a typical electrical currentcarried by the first metal layer 211 and/or the second metal layer 213.

FIG. 2B is a cross-sectional side view of the workpiece 202 at asubsequent stage after forming holes 203 extending at least partiallythrough the workpiece 202. An individual hole 203 is formed through thesubstrate pad 112 a, and the hole 203 includes an endwall 204, a firstsidewall 205 that is adjacent to the first metal layer 211, and a secondsidewall 206 that is adjacent to the second metal layer 213. In manyembodiments, an etching process forms the hole 203 using single- ormulti-step wet/dry etching techniques, laser drilling/ablation methodsand/or silicon machining techniques (e.g.,micro-electro-discharge-machining, abrasive machining, sand blasting,and/or cryogenic etches). The etching process can form the holes 203such that the first vias 215 (FIG. 2A) are removed from the workpiece202 and the selected first ESD devices 151 a are disconnected from theinternal circuitry 131 a. The etching process, however, does not removethe second vias 217 from the workpiece 202 so that the internalcircuitry 131 a remains electrically coupled to the substrate pads 112a. In other embodiments, the holes 203 can be formed other locations inthe workpiece 202 to disconnect the selected first ESD device 151 awithout removing the first vias 215. For example, in an alternativeembodiment, an etching process can form the holes 203 in the secondmetal layer 213 such that a portion of the second metal layer 213 isremoved from the workpiece 202 and the selected first ESD devices 151 aare electrically disconnected from the internal circuitry 131 a.

FIG. 2C is a cross-sectional side view of the workpiece 202 at asubsequent stage after forming a dielectric liner 122 along the endwall204 and the sidewalls 205 and 206 of the hole 203. The dielectric liner122 may initially be globally deposited on the workpiece 202, and awet/dry etch can remove portions of the dielectric layer 122 that arenot located within the hole 203. In many embodiments, the dielectricliner 122 includes a nonconductive material that can be deposited at lowtemperatures, such as materials that can be deposited using chemicalvapor and/or physical vapor deposition (CVD and/or PVD) processes. Forexample, the dielectric liner 122 can include a phosphosilicate glass(PSG) or other type of organic or inorganic dielectric coating material.

FIG. 2D is a cross-sectional side view of the workpiece 202 at asubsequent stage after forming the interconnects 120. A seed layer (notshown) can be formed on the surfaces of the dielectric liner 122 withinthe hole 203 (FIG. 2C), and individual metal layers 224 can be platedonto the seed layer. For example, the seed layer can be a conductivematerial, such as copper, and may receive an electrical potential forinitiating plating of the metal layer 224. In other embodiments,however, an electroless plating process can form the metal layer 224.Also, while the interconnect 120 is shown as being completely filled bythe metal layer 224, in other examples, the interconnect 120 may be onlypartially filled by the metal layer 224. For example, the interconnect120 can include an opening extending through the center of the metallayer 224. In many embodiments, the metal layer 224 can include copper,gold, nickel, and/or palladium.

FIG. 2E is a cross-sectional side view of the workpiece 202 at asubsequent stage after thinning the first substrate 110 a and depositingthe dielectric layer 114. The first substrate 110 a can be thinned usingchemical etching, backgrinding, chemical-mechanical polishing, and/orplasma thinning techniques. Such a process can be carried out in singleor multiple steps and can also include selectively removing substratematerial from the first substrate 110 a to define a projection portion227 of the interconnect 120. After thinning the first substrate 110, thedielectric layer 114 can be deposited at the back-side surface of thefirst substrate 110 a. For example, the dielectric layer 114 can bespun-on such that the dielectric layer 114 covers the back-side surfaceof the first substrate 110 a but does not cover the projection portionof the interconnect 227. In several embodiments, an additional etchingprocess can remove portions of the dielectric liner 122 from thesidewalls of the projection portion 227 using, for example, a dilutehydrofluoric (HF) etch. FIG. 2E also shows the redistribution layer 140including the RDL traces 142, the RDL contacts 144, and a passivationlayer 256 encapsulating the RDL traces 142 and defining locations of theRDL contacts 144.

FIG. 2F is a partially exploded, cross-sectional side view of theworkpiece 202 during inter-die bonding and the die singulation stage. Atthis stage, second die 102 is aligned with and electrically connected tothe first die 101 by forming the metal bonds 166 between the RDLcontacts 184 of the second die 102 and the interconnects 120 of thefirst die 101. The substrate 110 a may include fiducials or other typesof alignment markers for accurate alignment between the RDL contacts 184and the interconnects 120, and various types of direct bondingtechniques can be employed for forming the metal bonds 166. For example,bonding techniques such as copper-to-copper bonding, copper-to-tinbonding, oxide bonding, and electroplating may be used to electricallyintercouple the RDL connects 184 with the interconnects 120. The seconddie 102 can also be optionally attached to the first die 101 with anadhesive layer (not shown). After electrically connecting the second die102 to the first die 101, the first die 101 can be singulated from theworkpiece 202 via a die cutting process at substrate cutting lanes 248to separate the assembly of the first and second dies 101 and 102 fromthe workpiece 202. The assembly of the first and second dies 101 and 102can then be mounted and electrically coupled to a variety of substrates,such as the interposer substrate 190 (FIG. 1A). In other embodiments,this assembly can be coupled with other types of structures for carryingand/or electrically coupling with the first and second dies 101 and 102.

Alternative manufacturing techniques can be employed in other examplesof fabricating a workpiece. For example, FIG. 3 is a cross-sectionalside view showing an embodiment of a workpiece 302 carrying internalcircuitry 333, a temporary ESD device 335 a electrically isolated fromthe internal circuitry 333, and a permanent ESD device 335 belectrically coupled to the internal circuitry 333. The embodiment shownin FIG. 3 can be similar to the first die 101 shown in FIG. 1B. Thetemporary ESD device 335 a can be electrically isolated from theinternal circuitry 333 in a similar manner to that described withreference to FIGS. 2A-F. The permanent ESD device 335 b, on the otherhand, can provide ESD protection to the internal circuitry 333 duringsubsequent manufacturing of the workpiece 302. In several embodiments,the permanent ESD device 335 b has a smaller footprint than thetemporary ESD device 335 a and introduces less signal delay than thetemporary ESD device 335 a. Thus, the permanent ESD device 335 b may notbe as effective at ESD protection as the temporary ESD device 335 a, butthe permanent ESD device 335 b can provide a measure of ESD protectionduring manufacturing between the time when the temporary ESD device 335a is electrically isolated from the internal circuitry 333 and the timewhen the internal circuitry 333 is electrically coupled to the secondESD device 335 b of the second die 102 (FIG. 1A).

Embodiments of workpieces and stacked systems can also employinterconnects for electrically isolating integrated circuits and othertypes of circuit components, in addition to or in lieu of ESD devices.For example, FIG. 4 is a cross-sectional side view showing an embodimentof a workpiece 402 carrying a memory 433, a first memory component 435 aelectrically isolated from the memory 433, and a second memory component435 b electrically coupled to the memory 433. The memory 433, forexample, can be a programmable memory, and the process of forming theinterconnect 120 can be used to program the memory 433 by disabling thefunctionality of the first memory component 435 a. Such a programmingimplementation can be similar in nature to permanently programming afield programmable gate array (FPGA). However, instead of usingelectrical potentials to selectively hardwire the memory, the process offorming the interconnect can selectively hardwire the memory 433.

Any one of the microelectronic dies having ESD devices with disabledelectrical connections described above with reference to FIGS. 1A-4 canbe incorporated into any of a myriad of larger or more complex systems500, a representative one of which is shown schematically in FIG. 5. Thesystem 500 can include a processor 501, a memory 502 (e.g., SRAM, DRAM,Flash, or other memory device), input/output devices 503, or othersubsystems or components 504. Microelectronic devices may be included inany of the components shown in FIG. 5. The resulting system 500 canperform any of a wide variety of computing, processing, storage, sensor,imaging, or other functions. Accordingly, representative systems 500include, without limitation, computers or other data processors, forexample, desktop computers, laptop computers, Internet appliances,hand-held devices (e.g., palm-top computers, wearable computers,cellular or mobile phones, and personal digital assistants),multi-processor systems, processor-based or programmable consumerelectronics, network computers, and minicomputers. Other representativesystems 500 include cameras, light or other radiation sensors, serversand associated server subsystems, display devices, or memory devices. Insuch systems, individual dies can include imager arrays, such as CMOSimagers. Components of the system 500 may be housed in a single unit ordistributed over multiple, interconnected units, e.g., through acommunications network. Components can accordingly include local orremote memory storage devices and any of a wide variety ofcomputer-readable media.

From the foregoing, it will be appreciated that specific embodimentshave been described herein for purposes of illustration, but well-knownstructures and functions have not been shown or described in detail toavoid unnecessarily obscuring the description of the embodiments. Wherethe context permits, singular or plural terms may also include theplural or singular term, respectively. Moreover, unless the word “or” isexpressly limited to mean only a single item exclusive from the otheritems in reference to a list of two or more items, then the use of “or”in such a list is to be interpreted as including (a) any single item inthe list, (b) all of the items in the list, or (c) any combination ofthe items in the list. Additionally, the term “comprising” is usedthroughout to mean including at least the recited feature(s) such thatany greater number of the same feature or additional types of otherfeatures are not precluded.

It will also be appreciated that specific embodiments have beendescribed herein for purposes of illustration but that variousmodifications may be made within the claimed subject matter. Forexample, in addition to or in lieu of the redistribution layers,embodiments of the stacked system 100 can employ other types ofintra-die electrical couplings between dies or between a die and aninterposer substrate. In addition, the described methods of disablingelectrical connections to ESD devices can include various modifications.Referring to FIG. 1A, for example, electrical connections can bedisabled at metal layers located within the substrate 140 or at metallayers located within a redistribution layer 140. Furthermore, many ofthe elements of one embodiment can be combined with other embodiments inaddition to, or in lieu of, the elements of the other embodiments.Accordingly, the invention is not limited except as by the appendedclaims.

We claim:
 1. A system of stacked microelectronic dies, comprising: afirst microelectronic die including a backside, an integrated circuit,first electrostatic discharge (ESD) devices, and an interconnectextending through the first die to the backside, wherein theinterconnects are electrically coupled to the integrated circuit, andwherein selected first ESD devices are electrically isolated from theinterconnects; and a second microelectronic die including a front sidecoupled to the backside of the first die, a metal contact at the frontside electrically coupled to one of the interconnects, and a second ESDdevice electrically coupled to the metal contact, wherein the integratedcircuit of the first die is electrically coupled to the second ESDdevice.
 2. The system of claim 1, further comprising a metal bondcoupling the contact of the second die with one of the interconnects ofthe first die, wherein the second ESD device is electrically coupled tothe integrated circuit via the metal bond.
 3. The system of claim 1wherein the first die further includes a substrate carrying theintegrated circuit and the first ESD devices, and wherein theinterconnect is positioned in the substrate such that an electricalconnection between a selected first ESD device and the interconnect isdisabled.
 4. The system of claim 1, further comprising a dielectriclayer at least partially lining the interconnect and electricallyisolating a selected first ESD device from the interconnect.
 5. Thesystem of claim 1 wherein the integrated circuit is a first integratedcircuit, and wherein the second die includes a second integrated circuitelectrically coupled to the second ESD device.
 6. The system of claim 1,further comprising an interposer substrate carrying the first and seconddies, the interposer substrate including a metal pad electricallycoupled to the integrated circuit and the second ESD device, the metalpad also being electrically isolated from the first ESD devices.
 7. Amicroelectronic workpiece, comprising: a substrate having a front sideand a backside; a first circuit and a second circuit carried by thesubstrate, the first circuit having an integrated circuit, the secondcircuit having an electrostatic discharge (ESD) device; an interconnectextending through the substrate and electrically coupled to the firstcircuit, the interconnect having a metal layer electrically coupling thefront side of the substrate with the backside of the substrate; and adielectric liner along the interconnect between the interconnect and thesubstrate wherein the dielectric liner electrically isolates theintegrated circuit from the ESD device.
 8. The microelectronic workpieceof claim 7 wherein the dielectric liner separates the interconnect fromthe second circuit.
 9. An interconnect structure, comprising: a firstmetal layer of a microelectronic die, the microelectronic die having anintegrated circuit and an electrostatic discharge (ESD) device; a secondmetal layer of the die being separated from the first metal layer by atleast one passivation layer; a metal interconnect extending through thedie from, at least, a surface at a front side of the die to a surface ata backside of the die, the interconnect also extending through the firstmetal layer and the second metal layer; and a dielectric layer at leastpartially lining the interconnect and electrically isolating theintegrated circuit and the ESD device.
 10. The interconnect structure ofclaim 9 wherein the first metal layer provides a conduction path betweenthe integrated circuit and the interconnect, and the dielectric layerelectrically isolates a conduction path between the integrated circuitand the interconnect.
 11. The interconnect structure of claim 9 whereinthe second metal layer provides a conduction path to the ESD device, andthe dielectric layer electrically isolates the conduction path from thefirst metal layer.
 12. The interconnect structure of claim 9 wherein thefirst and second metal layers are located within a microelectronicsubstrate carried by the die.
 13. The interconnect structure of claim 9wherein the first and second metal layers are located within aredistribution layer attached to the surface at the front side of thedie.
 14. The system of claim 1 wherein the first microelectronic dieincludes a first metal layer and a second metal layer separated from thefirst metal layer by at least one passivation layer.
 15. The system ofclaim 14 wherein the first metal layer provides a conduction pathbetween the integration circuit and the interconnect.
 16. The system ofclaim 1 wherein the first microelectronic die includes a first metallayer, and wherein the first metal layer provides a first conductionpath between the integration circuit and the interconnect.
 17. Thesystem of claim 16 wherein the second microelectronic die includes asecond metal layer, and wherein the second metal layer provides a secondconduction path between the interconnect and the second ESD device. 18.The system of claim 1, further comprising a redistribution layerattached to the first microelectronic die.
 19. The system of claim 18wherein the redistribution layer includes a first metal layer and asecond metal layer separated from the first metal layer by at least onepassivation layer.
 20. The system of claim 19 wherein the first metallayer provides a conduction path between the integration circuit and theinterconnect.
 21. The microelectronic workpiece of claim 7 wherein thesubstrate is an interposer substrate having a metal pad electricallycoupled to the first circuit.
 22. The microelectronic workpiece of claim21 wherein the metal pad is electrically isolated from the secondcircuit.
 23. The microelectronic workpiece of claim 7, furthercomprising a redistribution layer attached to the substrate.
 24. Themicroelectronic workpiece of claim 23 wherein the redistribution layerincludes a first metal layer and a second metal layer separated from thefirst metal layer by at least one passivation layer.
 25. Themicroelectronic workpiece of claim 24 wherein the first metal layerprovides a conduction path between the first circuit and theinterconnect.
 26. The interconnect structure of claim 9, wherein the ESDdevice is a first ESD device, and wherein the interconnect structurefurther comprises a metal bond electrically coupling the metalinterconnect with a second ESD device.
 27. The interconnect structure ofclaim 9, further comprising an interposer substrate carrying themicroelectronic die, wherein the interposer substrate including a metalpad electrically coupled to the integrated circuit positioned within themicroelectronic die, and wherein the metal pad is electrically isolatedfrom the ESD device positioned within the microelectronic die.